Inductive electromotive force in inductance coil coil is always against current change in coil. Inductance coil on the AC current has a block effect, the size of the obstruction is called Inductance XL, the unit is ohm, it and the inductance amount L and alternating current F relationship is XL=2ΠFL, inductor can be divided into high-frequency resistance coil and low frequency resistance coil.

1. The function of tuning and frequency selection

Inductance coil and capacitor shunt can form LC tuning circuit. That is, the inherent oscillation frequency of the circuit is equal to the frequency f of the f0 signal, then the inductance of the loop is equal to the capacitive resistance, so the electromagnetic energy oscillates back and forth in the inductance and capacitance, which is the resonant phenomenon of LC loop.